Fluid system additive

ABSTRACT

A new fluid system additive is provided that serves to disperse and maintain fluid system solids in a stabilized condition and also “toughen” the filter cake. Fluid systems containing this additive also tolerate calcium contamination better than existing additives, and in laboratory tests simulating well conditions, the treated fluid systems demonstrate good fluid properties at high temperatures (e.g. 250° F.) in contrast to similar fluid systems treated with conventional, more costly additives.  
     In a preferred embodiment, a composition or additive for use in hydrocarbon exploitation includes a biopolymer derived from at least one species of the family Musaceae.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] Not Applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not Applicable.

BACKGROUND OF THE INVENTION

[0003] 1. Field of the Invention

[0004] The present invention generally relates to compositions of andmethods used for hydrocarbon exploitation such as the drilling andproduction of wells, especially oil and gas wells. More particularly,the invention relates to such compositions and methods, which alter thephysical or chemical properties of a fluid system, including additivesfor controlling fluid losses during hydrocarbon exploitation processes.

[0005] 2. Description of Related Art

[0006] In the drilling industry, a hollow drill pipe with a rotary bitattached to the lower end is typically rotated in a borehole to make anoil, gas, thermal or water well. A fluid system (e.g. drilling fluid or“mud”) is pumped down the hollow drill pipe, through the bit at thebottom of the borehole, and then up to the surface through the annularspace between the drill pipe and the borehole wall. The fluid systemlubricates and cools the rotating drill bit, suspends and carriescuttings out of the borehole, coats the wall of the hole with a thinimpervious layer of solid material to prevent flow of fluids into or outof the formation, and also exerts a hydrostatic pressure on theformation to counterbalance the pressure of liquids or gases presenttherein. Loss of fluid can occur due to porosity or cracks in theformation.

[0007] Typically, the fluid system is primarily a suspension of solidmaterial, such as clay, in a liquid such as water, but it may alsocontain a variety of additives or improvements. For the fluid system toperform its functions, it must have certain physical properties. Thefluid must have viscosity, and yet be readily pumpable. It must besufficiently thixotropic to suspend the cuttings in the borehole whenfluid circulation stops. The fluid must release cuttings from thesuspension when agitating in the settling pits. It must form a thinimpervious filter cake on the borehole wall to prevent loss of liquidfrom the fluid system by filtration into the formations.

[0008] A filter cake forms when the fluid system contains particles ofsize only slightly smaller than the size of the pore openings of theformation. Such a filter cake effectively seals the borehole wall toinhibit any tendencies of sloughing, heaving or cave-in of rock into theborehole. The liquid, which enters the formation while the cake is beingestablished, is known as the surge loss or spurt loss, while the liquid,which enters after the cake is formed, is known as the filtrate. Boththe spurt loss and filtration rate must be minimized when penetratingpotentially productive formations in order to minimize any damagingeffects from fluids entering the formation.

[0009] Further, the fluid must be capable of suspending high specificgravity weighting agents, such as barite or other inorganic heavy metalcompounds, to maintain sufficient pressure against a formation whennecessary. The fluid system should also be able to assimilate finelydivided drill cuttings formed during hydrocarbon exploitationoperations, and should be able to accept some chemical contaminateswithout excessively disrupting the physical properties of the fluidsystem.

[0010] To establish and maintain the desired physical properties, avariety of chemicals, clays and weight materials are added towater-based fluids. Rock particles and low-yielding clays are generallyincorporated into the fluid system to provide viscosity to the fluidsystem, to deposit a filter cake that will seal permeable formations inorder to limit filtration losses and prevent stuck pipe, and to providebuoyancy for drill cuttings. These solids also affect many fluid systemproperties adversely, however. As mentioned above, formation clays areunavoidably incorporated into the fluid system, and depending on theirnature and amount, the clay minerals can be beneficial or harmful to thefluid system. Because it is not possible to remove all drill solids,especially the very small, colloidal particles, either mechanically orby other means, they must be considered a continual contaminant of afluid system. Contaminants, such as gypsum, can “cut” the fluid systemcausing particles to flocculate and the viscosity to increase. When thisoccurs, there is danger of torquing the drill pipe to the point ofbreakage or of causing a blowout. At high temperatures, gelation orthickening of the fluid can occur, leading to greatly increased pressureon the recirculation pump. A balance of all the favorable and adverseeffects must be achieved in order for the fluid system to providepressure control to prevent an influx of formation fluid, provide energyat the bit to maximize rate of penetration, provide wellbore stabilitythrough pressured or mechanically stressed zones, suspend cuttings andweight material during static periods, permit separation of drilledsolids and gas at the surface, and to remove cuttings from the well.

[0011] Generally, the term “clay” is used to describe premium groundclay minerals, such as Wyoming bentonite, that are added to increasefluid viscosity and to improve filter cake. Drill cuttings, barite andother solids, however, will increase viscosity (resistance to flow),especially if the particle size degrades into the colloidal range.Colloidal solids produce most of the viscosity in fluid systems due tothis surface area increase. For that reason, the volume ofcolloidal-size solids contained in fluid systems must be controlled andthe cation exchange capacity, water adsorption and surface area of clayparticles must be taken into account in order to minimize hydrocarbonexploitation problems. Not only is the surface area of clay particlesimportant in determining a fluid's resistance to flow, the clay'schemical composition and its “activity” or electrical chargecharacteristics also affect how water and chemical contaminants ortreatments will interact with the clay particles to alter the fluid'sproperties.

[0012] In an attempt to avoid or to compensate for certain effects, avariety of fluid system additives have been used in the drillingindustry. Additives that reduce the spurt loss and filtration rate arereferred to as fluid loss control agents. Additives that reduce flowresistance and gel development in fluid systems are referred to asthinners or deflocculants. Some of these additive materials includestarches (e.g. corn, potato), starch derivatives, water solublecellulose derivatives, humates, plant tannins, polyphosphates orphosphate-containing materials, lignite materials, lignosulfonates andsynthetic polymers. One of the problems with some of those materials isthat they are unstable at the higher temperatures that are typicallyencountered downhole. Cost and environmental effects of the additivesare also important factors. What is needed is a commercially attractivemultifunctional fluid system additive, such as a fluid loss controladditive, that is capable of stabilizing the fluid properties over arange of temperatures and contaminant levels under hydrocarbonexploitation conditions.

SUMMARY OF PREFERRED EMBODIMENTS

[0013] A new fluid system additive is provided that serves to disperseand maintain fluid system solids in a stabilized condition and also“toughen” the filter cake. Fluid systems containing this additive alsotolerate calcium contamination better than existing additives, and inlaboratory tests simulating well conditions, the treated fluid systemsdemonstrate good fluid properties at high temperatures (e.g. 250° F.) incontrast to similar fluid systems treated with conventional, more costlyadditives.

[0014] The new fluid system additive may be used for hydrocarbonexploitation in both downhole (e.g. horizontal, vertical drilling) andin surface applications. The additive is not limited to drilling fluidapplications, and instead will find use in a variety of servicing (e.g.fracturing fluid), completion, workover, production, reclamation anddisposal operations.

[0015] In accordance with certain embodiments of the invention, acomposition for fluid loss control of fluid systems is provided whichincludes the flour of at least one species of the banana family,Musaceae. The banana flour may have varying starch to fiber ratios asdisclosed below, but preferably has a starch to fiber ratio of at least7:3. In certain embodiments, the banana flour is modified.

[0016] In accordance with yet another embodiment of the invention, acomposition for deflocculating or thinning fluid systems is providedwhich includes the flour of at least one species of the banana family.

[0017] In accordance with still another embodiment of the invention, acomposition for stabilizing fluid systems is provided which includes theflour of at least one species of the banana family.

[0018] In accordance with another embodiment of the invention, acomposition for viscosity modification of fluid systems is providedwhich includes the flour of at least one species of the banana family.

[0019] In accordance with still yet another embodiment of the invention,a composition for a loss control material that can rapidly sealformation fractures and/or inhibit the excessive loss of fluid systemsis provided which includes the flour of at least one species of thebanana family.

[0020] In accordance with another embodiment of the invention, acomposition for fracturing fluids is provided which includes the flourof at least one species of the banana family.

[0021] Also provided in accordance with the present invention is amethod of preventing loss of a fluid system. The method includes addingone of the above-described compositions to a fluid system. These andother embodiments, features and advantages of the present invention willbecome apparent with reference to the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] For a more detailed description of the preferred embodiment ofthe present invention, reference will now be made to the accompanyingdrawings, wherein:

[0023]FIG. 1 is a schematic representation illustrating differentfeatures which define the banana family;

[0024]FIG. 2 is a graph illustrating the filtration properties ofExample 9;

[0025]FIG. 3 is a graph illustrating the filtration properties ofExample 10;

[0026]FIG. 4 is a graph illustrating the filtration properties ofExample 12; and

[0027]FIG. 5 is a graph illustrating the swelling of contacting shale byvarious formulations.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0028] As stated above, conventional fluid system additives such asfluid loss control additives include starches and starch derivatives.Starches are carbohydrates of a general formula (C₆H₁₀O₅)n and arederived from corn, wheat, oats, rice, potatoes, yucca and similar plantsand vegetables. They consist of about 27% linear polymer (amylose) andabout 73% branched polymer (amylopectin). The two polymers areintertwined within starch granules. Granules are insoluble in coldwater, but soaking in hot water or under steam pressure ruptures theircovering and the polymers hydrate into a colloidal suspension. Thisproduct is a pregelatinized starch and has been used in fluid systemsfor many years. Amylose and amylopectin are nonionic polymers that donot interact with electrolytes.

[0029] Because conventional unmodified starches have thermal stabilityto about 250° F. and are subject to bacterial attack unless protected byhigh salinity or bacteriocide, the trend has been to modify orderivatize starches. Modification of starch can be achieved by chemicalor physical methods. Chemical methods include hydrolysis by enzyme oracid and chemical derivatization to impart more hydrophilic orhydrophobic properties. Physical methods include heat-moisture treatmentand annealing.

[0030] Derivatized starches, such as hydroxypropyl and carboxymethylstarches are currently used in drilling fluids and completion fluids.Being nonionic, hydroxypropyl (HP) starch is only slightly affected bysalinity and hardness in fluids. Linear and branched carbohydratepolymers in natural starch have three reactive OH groups on each glucoseunit. During manufacture, these polymers are reacted with propyleneoxide, adding hydroxypropyl (CH(OH)CH₂CH₃) groups at the OH positions byan ether linkage. By adding the hydroxypropyl groups, the HP starchbecomes more resistant to thermal degradation and bacterial attack.

[0031] As can be appreciated, the added time and cost to modify orderivatize starches is undesirable. However, due to thermal degradationand bacterial attack, fluid system manufacturers are given few options.With environmental agencies such as the EPA (Environmental ProtectionAgency) constantly imposing stricter limits, the types of derivativescapable of being used are dwindling.

[0032] The present invention offers an environmentally and costattractive alternative to current starch derivatives. New additives forimproving the properties of fluid systems preferably include a dry basemixture prepared by the flour of at least one species of the bananafamily, Musaceae.

[0033] The banana family (Musaceae) includes three genera: Musa, Ensete,and Musella. Together Musa, Ensete, and Musella comprise about 45species including Musa acuminata Colla, M. X paradisoaca (hybrid),Ensete ventricossum Cheesman (Abyssinian banana), Musa balbisina Colla,M ornata Roxb., M. textilis Nee, and Musella lasiocarpa. Common namesfor the Musa species include banana, bananier nain, canbur, curro, andplantain.

[0034] The banana family can be generalized by the followingcharacteristics in combination with FIG. 1. The leaves are alternate andvery large, with the proximal concentric, appressed sheathing portionscomprising a pseudotrunk from which the individual petioles and bladesdiverge. The blades are simple with a prominent midrib and numerouspenni-parallel lateral veins. Eventually, an inflorescence axis arisingfrom the corm grows upward through the channel formed by the overlappingleaf bases and produces a terminal series of large overlapping bracts,each of which subtends and hides a cymose cluster of flowers. As eachcyme reaches anthesis, the subtending bract reflexes to expose theflowers and eventually abscises from the inflorescence axis. The flowersare zygomorphic and functionally unisexual, the proximal ones beingfemale and the distal ones male. The perianth comprises 2 series of 6petaloid tepals, 5 of which are connate into a 5-lobed tube leaving oneinner segment free. The androecium usually consists of 5 fertile stamensand a staminode that is opposite the free tepal. The gynoecium consistsof a single compound pistil of 3 carpels, a single style, and aninferior ovary with 3 locules, each containing numerous axile ovules.The fruit is a berry, usually with a leathery, separable exocarp, orpeel.

[0035] In some embodiments, the flour is prepared from the fruit orflower portion of a member in the Musa species. In other embodiments,the flour is prepared from the fruit or flower portion in combinationwith the peel of a member in the Musa species. In still otherembodiments, the flour is prepared from the peel of a member in the Musaspecies. The dry powder formed can be readily dissolved in a widevariety of fluids, from fresh water to brines.

[0036] A preferred method of preparing banana flour from unripenedbananas follows. Both a dry process and a wet process may produce thebanana flour. In a preferred embodiment, the banana is frozen beforepeeling in order to provide white color starch.

[0037] In the dry process, the unripened banana is preferably frozen at0° C. for 24 hours in order to destroy the polyphenol oxidase, whichaffects the browning of the starch. After freezing, the banana ispreferably defrosted by standing at room temperature, and is cut intosmall pieces or chips and dried in an oven. The dried chips arepreferably ground into powder and sieved.

[0038] Once sieved, the banana flour is suspended in a basic solution(e.g. NaOH) and any protein is removed using a centrifugal separator.The starch dispersion may be adjusted by varying the pH of the flour(e.g. by adding diluted HCl). After adjusting the starch dispersion, theflour is preferably centrifuged, forming a flour cake, which is dried at50° C. for 24 hrs. The dried flour cake is preferably milled and sieved.

[0039] As stated above, the flour may be unmodified (natural) ormodified. It is believed that the prepared banana flour contains between70-90% starch. In some embodiments, it may be desirable to isolateand/or purify the starch via modification. Modification may be performedby conventional methods (e.g. physical, chemical) to increase themolecular weight of the starch, for example. It is contemplated thatmodified banana starches may have enhanced thermal resistance (350-400°F.+) and Theological properties. In a preferred embodiment, the bananastarches are substantially stable at these high temperatures.Substantially stable is herein defined as not readily altering inchemical makeup or physical state.

[0040] Drilling muds containing the above-described additives wereevaluated in laboratory tests designed to simulate typical to severewell conditions, and their physical properties were compared under thesame test conditions to identical muds containing conventionaladditives.

EXAMPLES 1-2

[0041] Treated muds were prepared as follows: A fluid consisting ofnatural and modified biopolymers (including a predetermined amount ofbanana flour prepared by the dry process described above), buffer,defoamer and other salts in water was sheared for 45 minutes at highspeed in a Hamilton Beach Mixer, and then aged for 2 hours in a sealedcontainer at room temperature. After aging, a bridging agent andviscosifier were added and the ingredients were sheared for 30 minutesat high speed. The resultant slurry was hot rolled for 16 hours at 170°F. to stabilize the fluid and to allow full hydration of thebiopolymers, salts and other solids.

[0042] Conventional muds (Dual Flo and FloTrol), which contain modifiedstarches from known plants such as potatoes and corn, have beensimilarly prepared, with the exception that the conventional modifiedstarches replaced the banana flour of the treated muds.

[0043] The compositions of the resultant mud formulations (Examples 1-2,Dual Flo 1, and Flo Trols 1-2) are shown in Table 1. The Theological andfiltration properties of the resultant mud formulations were thendetermined and are reported in Table 2. To determine rheologicalproperties, the samples were mixed and heat aged (static/dynamic) for 16or more hours. A viscometer (Fann Model 35 or Brookfield) was employedto measure the plastic viscosity (PV), yield point (YP) and low shearrate viscosity (LSRV) of the samples. To determine the filtration rate,static and/or dynamic testing was performed using conventional tools(i.e. HPHT test cells, Fann Model 90 filtration apparatus, paper API).

[0044] Benchmark rheological values for a drilling mud include a PVbetween 10 cp and 40 cp, a YP between 10 lb/100 ft and 40 lb/100 ft, anda LSRV between 15K and 70K, as indicated by the conventional samples.Benchmark filtration values for a drilling mud include a spurt valuebetween 0 and 5 cc and a value of least 10 cc after 30 minutes.Referring still to Table 2, the mud containing the banana flour additiveprovided the better overall mud properties under the stated testconditions than the more expensive comparative commercial product. TABLE1 Conventional Mud Composition Comparison Dual Flo #1 Flo Trol #1 Ex #1Flo Trol #2 Ex #2 Vol Lab Vol Lab Vol Lab Vol Lab Specific Conc (per VolConc (per Vol Conc (per Vol Conc (per Vol Conc Vol Lab Vol ProductGravity (ppb) bbl) (ml) (ppb) bbl) (ml) (ppb) bbl) (ml) (ppb) bbl) (ml)(ppb) (per bbl) (ml) FloVis NT* 1.5 0.75 0.001 0.500 0.75 0.001 0.5000.75 0.001 0.500 1 0.002 0.667 1 0.002 0.667 Dual Flo 1.5 5 0.010 3.333X X X X FloTrol 1.5 X** 5 0.010 3.333 X 5 0.010 3.333 X GBTrol 0.24 X X5 0.060 20.833 X 5 0.060 20.833 (Banana Flour) MgO 3.65 1 0.001 0.274 10.001 0.274 1 0.001 0.274 1 0.001 0.274 1 0.001 0.274 ECF-590 1.2 10.002 0.833 1 0.002 0.833 1 0.002 0.833 1 0.002 0.833 1 0.002 0.833SafeCarb 2.8 30 0.031 10.714 30 0.031 10.714 30 0.031 10.714 30 0.03110.714 30 0.031 10.714 Product wt 37.75 37.75 37.75 38.00 38.00 (lb/bbl)Product vol 0.05 0.04 0.09 0.05 0.10 (bbl/bbl) Total lab vol 15.65 20.7133.15 15.82 38.37 (ml/sample) Desired 11.80 11.80 1.80 11.80 11.80 finaldensity (ppg) Density of 11.60 11.60 11.60 11.60 11.60 liq fraction(ppg) Vol of liq 0.955 0.955 0.905 0.954 0.905 fraction (bbl/bbl)

[0045] TABLE 2 Conventional Mud Rheology/Filtration Comparison Dual Flo#1 Flo Trol #1 Ex #1 Flo Trol #2 Ex #2 After After After After AfterRheology Start Hot Rolling Start Hot Rolling Start Hot Rolling Start HotRolling Start Hot Rolling Temperature, ° F. 120 170 120 170 120 170 120250 120 250 600 rpm dial 50 51 55 53 48 56 55 52 56 62 reading 300 rpmdial 37 38 40 39 32 36 40 38 40 42 reading 200 rpm dial 31 32 32 33 2630 32 33 32 38 reading 100 rpm dial 24 25 24 26 20 22 24 25 24 26reading 6 rpm dial 11 11 12 12 7 7 12 12 9 10 reading 3 rpm dial 9 9 1010 6 6 10 10 7 8 reading Init. (10 sec) Gel 9 9 10 10 6 6 10 10 7 8Strength, lb/100 ft 10 min. Gel 10 10 12 11 7 7 12 12 9 9 Strength,lb/100 ft Plastic Viscosity, 13 13 15 14 16 20 15 14 16 20 cp YieldPoint, 24 25 25 25 16 16 25 24 24 22 lb/100 ft 1 min. Low shear   53 K39.1 K 24.7 K 38.3 K 32.8 K rate velocity 2 min. Low shear 47.7 K 37.6 K24.4 K 37.9 K 31.7 K rate velocity 3 min. Low shear 45.3 K   36 K 24.1 K37.7 K 28.9 K rate velocity PH 9.5 9.4 9.3 9.2 8.9 9.1 9.5 9.4 9.3 9.2Filtration Rate (vol/time) 30 sec 2.8 ml 3.2 ml 3.0 ml  1 min 3.0 ml 3.3ml 3.0 ml 30 min 7.2 ml 7.0 ml 3.1 ml 60 min 9.6 ml 8.2 ml 3.1 ml

EXAMPLES 3-7

[0046] Examples 3-7 are samples of additional treated muds, preparedaccording to the above-described method, using various amounts of bananaflour. The compositions of the resultant mud formulations are shown inTable 3. The function of various products named in Table 3 is listed inTable 4. Also listed in Table 4 are optional additives commonly used indrilling mud compositions and their functions. The rheologicalproperties of the resultant mud formulations were then determined andare reported in Table 5. TABLE 3 Composition of Treated Mud as FluidLoss Controller CONCENTRATION OF PRODUCT KCL CACL₂ FLUID TYPE DENSITYECF-688 (3%) BIOVIS SAFECARB KOH MGO NACL (11.6 PPG) CABR₂ SAMPLE (RDF)(PPG) (LB/BBL) (BBL) (LB/BBL) (LB/BBL) (LB/BBL) (LB/BBL) (BBL) (BBL)(BBL) EX #3 BIOVIS/STARCH 8.8 4 0.929 1.5 32 0.25 (KCL) EX #4BIOVIS/STARCH 9.8 4 1.5 32 1 0.929 (NACL) EX #5 BIOVIS/STARCH 9.5 4 1.532 1 0.871 (CACL₂) EX #6 BIOVIS/STARCH 9.9 4 1.5 32 1 0.943 (CACL₂) EX 7BIOVIS/STARCH 11.5 4 1.5 32 1 0.971 (CACL₂)

[0047] TABLE 4 Product Function Product Function ECF-688 (Banana Flour)To be determined Duovis (Xanthan gum) Viscosifier BioVis (Scleroglucan)Viscosifier DualFlo (Modified starch) Fluid loss additive SAFECARB(Calcium carbonate) Sealant & weight agent KCl MgO, Buffer, pH controlCitric Acid Buffer, pH control KOH Buffer, pH control NaCl CaCl₂ CaBr₂KHCO₂ K-Formate Glydril (glycol) Shale inhibitor/stabilizer

[0048] TABLE 5 Rheology of Treated Mud as Fluid Loss Controller Ex #3 Ex#4 Ex #5 Rheology Start After Hot Rolling Start After Hot Rolling StartAfter Hot Rolling Temperature, ° F. 120 150 210 250 120 150 210 250 120150 210 250 600 rpm dial reading 37 42 40 35 72 74 75 Deg 50 52 49 Deg300 rpm dial reading 28 30 28 24 48 50 53 ″ 35 36 33 ″ 200 rpm dialreading 24 23 23 20 38 40 43 ″ 30 28 25 ″ 100 rpm dial reading 19 18 1715 26 27 30 ″ 21 22 18 ″  6 rpm dial reading 10 7 6 5 10 8 9 ″ 8 6 5 ″ 3 rpm dial reading 9 6 5 4 8 7 7 ″ 7 5 4 ″ Init. (10 sec) Gel 9 6 5 4 87 7 ″ 7 5 4 Strength, lb/100 ft 10 min. Gel 10 8 6 5 9 8 8 ″ 8 6 5Strength, lb/100 ft Plastic Viscosity, cp 9 12 12 11 24 24 22 ″ 15 16 16″ Yield Point, lb/100 ft 19 18 16 13 24 26 31 ″ 20 20 17 ″ 1 min. Lowshear 32 K 22 K 13 K 10 K 24 K 25 K 30 K ″ 16 K 18 K 10 K ″ ratevelocity 2 min. Low shear 30 K 22 K 14 K 11 K 20 K 20 K 30 K ″ 15 K 17 K10 K ″ rate velocity 3 min. Low shear 29 K 22 K 14 K 12 K 19 K 19 K 29 K″ 15 K 16 K  9 K ″ rate velocity PH 10.4 10.2 10.2 10.2 9.9 9.6 9.6 9.68.4 8.2 8.2 Ex #6 Ex #7 Rheology Start After Hot Rolling Start After HotRolling Temperature, ° F. 120 150 210 250 120 150 210 250 600 rpm dialreading 69 80 65 Deg 110 129 95 Deg 300 rpm dial reading 45 52 40 ″ 7580 61 ″ 200 rpm dial reading 37 41 32 ″ 56 61 47 ″ 100 rpm dial reading27 28 21 ″ 37 40 31 ″  6 rpm dial reading 11 8 4 ″ 14 12 8 ″  3 rpm dialreading 9 7 3 ″ 12 10 6 ″ Init. (10 sec) Gel 9 7 3 ″ 12 10 6 ″ Strength,lb/100 ft 10 min. Gel 10 9 4 ″ 13 11 7 ″ Strength, lb/100 ft PlasticViscosity, cp 24 28 25 ″ 35 49 34 0 Yield Point, lb/100 ft 21 24 15 ″ 4031 27 0 1 min. Low shear 25 K 17 K 6 K ″ 30 K 33 K 9 K ″ rate velocity 2min. Low shear 25 K 17 K 4 K ″ 29 K 28 K 9 K ″ rate velocity 3 min. Lowshear 24 K 16 K 5 K ″ 28 K 27 K 9 K ″ rate velocity PH 8.4 8.3 8.3

EXAMPLES 8-14

[0049] Examples 8-14 are samples of additional treated muds, preparedaccording to the above-described method, using various amounts of bananaflour. The compositions of the resultant mud formulations are shown inTable 6. The rheological properties of the resultant mud formulationswere then determined and are reported in Table 7.

[0050] In Tables 6 and 7, a banana flour additive was evaluated as aviscosifier and fluid loss controller. Referring to Examples 13 and 14,the compositions are in the form of viscous, solids-free (SF) pills.Solids-free is herein defined as containing less than about 10% volumeof solids. The gelling properties of these pills suggest thatcompositions prepared with a banana flour additive may be used as a losscirculation material (LCM).

[0051] Referring still to Table 7, Example #10 provided the betteroverall mud properties under the stated test conditions than othertreated mud samples. As can be appreciated from Table 7, the bananaflour additive may be used alone or with other additives in synergisticways. TABLE 6 Composition of Treated Mud as Viscosifier and Fluid LossController CONCENTRATION OF PRODUCT ECF- FLUID 688 KCL CITRIC K-FORMATECABR₂ MGO TYPE DENSITY (LB/ (LB/ DUOVIS KOH ACID SAFECARB KHCO₂ (12.5PPG) (14.2 PPG) (LB/ SAMPLE (RDF) (PPG) BBL) BBL) (LB/BBL) (LB/BBL)(LB/BBL) (LB/BBL) (BBL) (BBL) (BBL) BBL) Ex #8 FLOPRO 8.8 4 10.7 1 0.250.25 32 NT (KCl) Ex #9 FLOPRO 12.2 3 1 0.25 0.25 32 0.929 NT (K-Citrate) Ex #10 FLOPRO 12.2 3 1 0.25 0.25 32 0.943 NT (K- Formate) Ex#11 FLOPRO 14.0 4 32 0.943 1 NT (CaBr₂) Ex #12 FLOPRO 14.05 4 32 0.971 1NT (CaBr₂) Ex #13 Viscous 13.80 12 0.971 1 Pills SF (CaBr₂) Ex #14Viscous 14.02 4 0.971 1 Pills SF (CaBr₂)

[0052] TABLE 7 Rheology of Treated Mud as Viscosifier and Fluid LossController Ex #8 Ex #9 Ex #10 Ex #11 Rheology Start After Hot RollingStart After Hot Rolling Start After Hot Rolling Start After Hot RollingTemperature, ° F. 120 150 210 250 120 150 210 250 300 120 150 210 250300 120 150 210 250 600 rpm dial 37 42 40 35 51 55 56 50 95 96 93reading 300 rpm dial 28 30 28 24 30 36 38 33 70 66 62 reading 200 rpmdial 24 23 23 20 23 28 32 27 54 53 49 reading 100 rpm dial 19 18 17 1513 20 23 19 39 38 33 reading  6 rpm dial 10 7 6 5 3 7 9 7 12 11 9reading  3 rpm dial 9 6 5 4 2 6 8 6 10 9 7 reading Init. (10 sec) Gel 96 5 4 2 6 8 6 10 9 7 Strength, lb/100 ft 10 min. Gel 10 8 6 5 3 7 9 7 1213 8 Strength, lb/100 ft Plastic Viscosity, cp 9 12 12 11 21 0 0 0 19 180 0 0 17 0 25 30 31 Yield Point, lb/ 19 18 16 13 9 0 0 0 17 20 0 0 0 160 45 36 31 100 ft 1 min. Low shear 32 K 22 K 13 K 10 K 8 K 30 K 15 K 51K 59 K 17 K rate velocity 2 min. Low shear 30 K 22 K 14 K 11 K 8 K 28 K14 K 46 K 64 K 17 K rate velocity 3 min. Low shear 29 K 22 K 14 K 12 K 9K 28 K 14 K 45 K 64 K 16 K rate velocity PH 10.4 10.2 10.2 10.2 9.9 9.69.4 9.1 7.9 7.9 7.9 Ex #12 Ex #13 Ex #14 Rheology Start After HotRolling Start After Hot Rolling Start After Hot Rolling Temperature, °F. 120 150 210 250 120 150 210 250 300 120 150 210 250 300 600 rpm dial108 125 106 49 67 reading 300 rpm dial 75 95 68 30 43 reading 200 rpmdial 62 77 53 23 33 reading 100 rpm dial 46 57 35 14 22 reading  6 rpmdial 17 20 10 4 6 reading  3 rpm dial 13 15 9 3 5 reading Init. (10 sec)Gel 13 15 9 3 5 Strength, lb/100 ft 10 min. Gel 14 19 10 4 6 Strength,lb/100 ft Plastic Viscosity, cp 0 33 30 0 0 38 0 0 0 0 19 24 0 0 YieldPoint, lb/ 0 42 65 0 0 30 0 0 0 0 11 19 0 0 100 ft 1 min. Low shear 48 K59 K 29 K >100 K 13 K 23 K rate velocity 2 min. Low shear 48 K 60 K 27K >100 K 12 K 23 K rate velocity 3 min. Low shear 47 K 60 K 24 K >100 K11 K 22 K rate velocity PH 7.9 7.8 7.8 7.2 7.4

[0053] In addition to rheological properties, filtration rate is aparameter of interest. As discussed in the background section, both thespurt loss and filtration rate must be minimized when penetratingpotentially productive formations in order to minimize any damagingeffects from fluids entering the formation. FIG. 2, Table 8 and FIG. 3,Table 9, and FIG. 4 illustrate the filtration rate and relatedproperties of Examples 9, 10, and 12 respectively.

[0054] Referring initially to FIG. 2 and Table 8, the Cake Deposit Index(CDI) of Example 9 (K-Citrate system) is high and the Dynamic FiltrationRate (DFR) is low. Also, in comparison with FIG. 3, the Dynamic Filtrate(DF) of the K-Citrate system is lower than in the K-Formate system.

[0055] Referring still to FIG. 3 and Table 9, the CDI of Example 10(K-Formate system) is low. This indicates that the formation of thefilter cake has almost reached steady state. Therefore, any additionalcake that will be deposited will not affect the DFR. TABLE 8 FiltrationProperties of Ex #9 Ex #9 (K-Citrate) Property Value Dynamic Filtrate(DF) 1 hr, ml 14.3 Dynamic Filtration Rate (DFR), ml-min 0.24 CakeDeposition Index (CDI), ml-hr² 17.1 Time interval, min 60.0 Avg Temp, °F. 300.2 Aloxite Core, μm 20.0 Avg Δ Pressure, psi 502.2 Spurt lossafter 8 sec 1.03

[0056] TABLE 9 Filtration Properties of Ex #10 Ex #10 (K-Formate)Property Value Dynamic Filtrate (DF) 1 hr, ml 20.5 Dynamic FiltrationRate (DFR), ml-min 0.34 Cake Deposition Index (CDI), ml-hr² 3.4 Timeinterval, min 60.0 Avg Temp, ° F. 300.6 Aloxite Core, μm 20.0 Avg ΔPressure, psi 500.9 Spurt loss after 10 sec 2.71

[0057] In addition to the above rheological and filtration properties,pH, filter cake thickness, solubility of filter cake in differentbreakers (acids, oxidizers, enzymes) is also of interest. For example,an acid solubility test (ASTM D3042) was performed on a banana floursample, where the testing procedure included immersing the mentionedsample in 15% HCl, boiling the sample, and filtering the sample througha 0.45-micron filter. The sample proved to be 95.1% soluble. Thisprovides insight that compositions prepared with a banana flour additivemay be used in fracturing fluids due to carrying properties and easybreaking with acid.

[0058] Additional testing performed includes contamination testing (e.g.from sea water, excess drilled solids, and excess barite) and dispersionand swelling of contacting rock (Shale). Referring now to Table 10,contamination testing for various materials is shown. Table 11 lists theformulation of the base fluid in Table 10. TABLE 10 ContaminationTesting Base Fluid Base Fluid + Base Fluid + Base Fluid + (8.4 Lb/gal)135 lb Barite 10% Drilled Solids 10% Sea Water Rheology Start After HotRolling Start After Hot Rolling Start After Hot Rolling Start After HotRolling Temperature, ° F. 120 150 120 150 120 150 120 150 600 rpm dialreading 36 36 57 52 47 40 35 34 300 rpm dial reading 26 26 41 39 35 3025 24 200 rpm dial reading 22 23 34 33 30 26 20 19 100 rpm dial reading17 18 26 25 23 20 15 14 6 rpm dial reading 7 8 10 9 9 8 6 5 3 rpm dialreading 6 6 8 7 8 6 5 4 Init. (10 sec) Gel Strength, 6 6 8 7 8 6 5 4lb/100 ft 10 min. Gel Strength, lb/100 ft 6 7 9 8 8 7 6 5 PlasticViscosity, cp 10 10 16 13 12 10 11 10 Yield Point, lb/100 ft 16 16 25 2627 20 14 14 PH 9.5 9.4 9.5 9.4 9.5 9.4 9.5 9.4

[0059] TABLE 11 Base Fluid Composition Base Fluid Concentration ECF-6884 lb/bbl MgO 1 lb/bbl DuoVis 1 lb/bbl SafeCarb 32 lb/bbl KCl 10.7 lb/bblCitric Acid 1 lb/bbl Water 0.971 bbl Biocide 0.25 lb/bbl

[0060] Table 12 and FIG. 5 illustrate the swelling of contacting shaleand Table 13 lists the results of a dispersion test using theformulations of Table 12. TABLE 12 Formulations for Swelling TestingConcentration K- Citric Density ECF-688 MgO DuoVis SafeCarb Citrate AcidWater Biocide Formulation (ppg) (lb/bbl) (lb/bbl) (lb/bbl) (lb/bbl)(lb/bbl) (lb/bbl) (bbl) (lb/bbl) #1 10.3 8 1 1 0 140 1 0.971 0.25 #210.3 4 1 1 32 100 1 0.971 0.25

[0061] TABLE 13 Dispersion Test Results Formulation % Recovery #1 89 #293 Water 2

[0062] The swelling testing was performed using a swell-meter on a shaleformation material in the form of compressed pellets (5 g/25,000 psi).The dispersion test was performed after the formulations had been hotrolled for 16 hours at 150° F. The % Recovery of the dispersion test isrelated to the drill cuttings retained by a U.S. mesh #30 sieve.

[0063] As shown in FIG. 5, both Formulation #1 and #2 have a markedlylower swelling percentage than water in shale. Compared to water,Formulation #1 has approximately a 67% swelling reduction andFormulation #2 has approximately a 71% swelling reduction. Referringback to Table 13, Formulation #1 and #2 also have a much higher recoverypercentage than water.

[0064] A unique property of mud compositions prepared with variousamounts of banana flour additive described above is that they stilldemonstrate good fluid properties even after being subjected to a 250°F. temperature for reasonable and expected intervals during operations,similar to muds that were prepared with conventional additives (i.e.modified starches). The preferred additives of the present invention aresuited for adding to fluid systems used in hydrocarbon exploitationoperations. Because the filter cake that results is firmer and moreslippery than with conventionally treated muds, fluid systems containingthe new additives are also expected to facilitate hydrocarbonexploitation. Without wishing to be limited to a particular theory, itis believed that the components of the additive thin the mud (i.e.,reduce the viscosity or resistance to flow) primarily by decreasing theelectrochemical forces between the solid particles and causingdeflocculation and dispersion of the solids. It is expected that fluidsystems containing the new additive will have desirable Theological andfluid loss properties in the field after exposure to shear, elevatedtemperature and after incorporation of additional drill solids andchemical contaminants.

[0065] In addition, while the banana additive has been tested for use indrilling fluids, it is believed that the banana additive will besuccessful in other hydrocarbon exploitation operations includingcompositions used in servicing, completion, workover, production,reclamation and disposal operations. Particular uses of interest includeas an additive in fracturing fluids and as an additive for formationsealing fluids. Also, because the banana additive is a natural source ofpotassium, it may be used to inhibit formation swelling.

[0066] Although the banana flour additive has been described for use inan aqueous-based fluid and in a viscous, solids-free pill, it isrecognized that any suitable vehicle for carrying the banana flouradditive to its desired location may be used. For example, any waterbased fluid or solid medium may be used. It is also contemplated thatoil based fluids may be used. Fluid is herein defined as a continuous,amorphous substance whose molecules move freely past one another andthat has the tendency to assume the shape of its container (i.e. aliquid or gas). It will be understood that fluid mediums includecolloidal and colloidal-like systems (e.g. gels). Solid is hereindefined as a substance that is held in a fixed form by cohesion amongits particles. It will be understood that solid mediums includeparticulate systems such as sand.

[0067] While the preferred embodiments of the invention have been shownand described, modifications thereof can be made by one skilled in theart without departing from the spirit and teachings of the invention.The embodiments described herein are exemplary only, and are notintended to be limiting. Many other variations and modifications of theinvention disclosed herein are possible and are within the scope of theinvention. For example, in addition to aging and bridging agents,viscosifiers, lubricants, corrosion inhibitors, oxygen scavenger, etc.may be added to the present fluid systems. The disclosures of allpublications, patents and patent applications cited above are herebyincorporated herein by reference.

What is claimed is:
 1. A fluid system for use in hydrocarbonexploitation comprising: a continuous liquid phase; and a biopolymerderived from at least one species of the family Musaceae.
 2. The fluidsystem according to claim 1 wherein the biopolymer is derived from thegenus Ensete.
 3. The fluid system according to claim 1 wherein thebiopolymer is derived from the genus Musella.
 4. The fluid systemaccording to claim 1 wherein the biopolymer is derived from the genusMusa.
 5. The fluid system according to claim 4 wherein theMusaceae-derived biopolymer comprises Musa flour.
 6. The fluid systemaccording to claim 5 wherein the Musa flour is prepared from a componentof the group consisting of fruit, peel, or combinations thereof.
 7. Thefluid system according to claim 5 wherein the Musa flour has a starch tofiber ratio of about 7:3 or greater.
 8. The fluid system according toclaim 5 wherein the Musa flour comprises at least 70% starch.
 9. Thefluid system according to claim 5 wherein the Musa flour comprises atleast 80% starch.
 10. The fluid system according to claim 1 wherein theMusaceae-derived biopolymer is unmodified.
 11. The fluid systemaccording to claim 10 wherein the rheological properties of said fluidsystem are substantially stable over a temperature range of about 120°F. to 250° F.
 12. The fluid system according to claim 1 wherein theMusaceae-derived biopolymer is chemically or physically modified. 13.The fluid system according to claim 12 wherein the rheologicalproperties of said fluid system are substantially stable at about 350°F.
 14. The fluid system according to claim 12 wherein the rheologicalproperties of said fluid system are substantially stable at temperaturesgreater than 400° F.
 15. The fluid system according to claim 1 furthercomprising a filter cake that contains the Musaceae-derived biopolymer.16. The fluid system according to claim 15 wherein the filter cake hasfiltration properties that are substantially stable at about 250° F. 17.The fluid system according to claim 1 wherein the continuous liquidphase comprises a gelled continuous liquid phase structure.
 18. Thefluid system according to claim 1 wherein the Musaceae-derivedbiopolymer comprises a fluid loss control additive.
 19. The fluid systemaccording to claim 1 wherein the Musaceae-derived biopolymer comprises afluid thinning additive.
 20. The fluid system according to claim 1wherein the Musaceae-derived biopolymer comprises a thermal resistanceadditive.
 21. The fluid system according to claim 1 further comprisingat least one component chosen from the group consisting of viscosifiers,biopolymers other than the Musaceae-derived biopolymer, thinners,bridging agents, aging agents, lubricants, corrosion inhibitors, andoxygen scavengers.
 22. The fluid system according to claim 1 wherein thefluid system is a drilling fluid.
 23. The fluid system according toclaim 1 wherein the fluid system is a servicing fluid.
 24. The fluidsystem according to claim 1 wherein the fluid system is a fracturingfluid.
 25. The fluid system according to claim 1 wherein theMusaceae-derived biopolymer comprises a loss circulation material. 26.The fluid system according to claim 25 wherein the loss circulationmaterial comprises a substantially solids-free pill.
 27. The fluidsystem according to claim 25 wherein the loss circulation materialassists in effectively sealing a formation.
 28. The fluid systemaccording to claim 25 wherein the rheological properties of said losscirculation material are substantially stable over a temperature rangeof about 120° F. to 250° F.
 29. The fluid system according to claim 25wherein the Musaceae-derived biopolymer is chemically or physicallymodified such that the Theological properties of said loss circulationmaterial are substantially stable at about 350° F.
 30. A method ofdrilling a well, comprising: injecting a fluid system into the well,wherein the fluid system comprises a continuous liquid phase and abiopolymer derived from at least one species of the family Musaceae. 31.The method according to claim 30 further comprising permitting the fluidsystem to form a filter cake.
 32. The method according to claim 31wherein the filter cake has filtration properties that are substantiallystable at about 250° F.
 33. The method according to claim 30 wherein theMusaceae-derived biopolymer is unmodified.
 34. The method according toclaim 33 wherein the Theological properties of said fluid system aresubstantially stable over a temperature range of about 120° F. to 250°F.
 35. The method according to claim 30 wherein the Musaceae-derivedbiopolymer is chemically or physically modified.
 36. The methodaccording to claim 35 wherein the rheological properties of said fluidsystem are substantially stable at about 350° F.
 37. The methodaccording to claim 35 wherein the rheological properties of said fluidsystem are substantially stable at temperatures greater than 400° F. 38.The method according to claim 30 further comprising at least onecomponent chosen from the group consisting of viscosifiers, biopolymersother than the Musaceae-derived biopolymer, thinners, bridging agents,aging agents, lubricants, corrosion inhibitors, and oxygen scavengers.39. The method according to claim 30 wherein the Musaceae-derivedbiopolymer comprises a source of potassium.
 40. A method of servicing awell, comprising: injecting a fluid system into the well, wherein thefluid system comprises a continuous liquid phase and a biopolymerderived from at least one species of the family Musaceae.
 41. The methodaccording to claim 40 further comprising permitting the fluid system toform a filter cake.
 42. The method according to claim 41 wherein thefilter cake has filtration properties that are substantially stable atabout 250° F.
 43. The method according to claim 40 wherein theMusaceae-derived biopolymer is unmodified.
 44. The method according toclaim 43 wherein the rheological properties of said fluid system aresubstantially stable over a temperature range of about 120° F. to 250°F.
 45. The method according to claim 40 wherein the Musaceae-derivedbiopolymer is chemically or physically modified.
 46. The methodaccording to claim 45 wherein the rheological properties of said fluidsystem are substantially stable at about 350° F.
 47. The methodaccording to claim 45 wherein the rheological properties of said fluidsystem are substantially stable at temperatures greater than 400° F. 48.The method according to claim 40 further comprising at least onecomponent chosen from the group consisting of viscosifiers, biopolymersother than the Musaceae-derived biopolymer, thinners, bridging agents,aging agents, lubricants, corrosion inhibitors, and oxygen scavengers.49. The method according to claim 40 wherein the Musaceae-derivedbiopolymer comprises a source of potassium.
 50. A composition for use inhydrocarbon exploitation comprising: a biopolymer derived from at leastone species of the family Musaceae; and a suitable vehicle for carryingthe biopolymer to a predetermined location.
 51. The compositionaccording to claim 50 wherein the Musaceae-derived biopolymer isunmodified.
 52. The composition according to claim 51 wherein therheological properties of said composition are substantially stable overa temperature range of about 120° F. to 250° F.
 53. The compositionaccording to claim 50 wherein the Musaceae-derived biopolymer ischemically or physically modified.
 54. The composition according toclaim 53 wherein the rheological properties of said composition aresubstantially stable at about 350° F.
 55. The composition according toclaim 53 wherein the rheological properties of said composition aresubstantially stable at temperatures greater than 400° F.
 56. Thecomposition according to claim 50 further comprising a filter cake thatcontains the Musaceae-derived biopolymer.
 57. The composition accordingto claim 56 wherein the filter cake has filtration properties that aresubstantially stable at about 250° F.
 58. The composition according toclaim 50 further comprising at least one component chosen from the groupconsisting of viscosifiers, biopolymers other than the Musaceae-derivedbiopolymer, thinners, bridging agents, aging agents, lubricants,corrosion inhibitors, and oxygen scavengers.
 59. The compositionaccording to claim 50 wherein the composition is a drilling fluid. 60.The composition according to claim 50 wherein the composition is aservicing fluid.
 61. The composition according to claim 50 wherein theMusaceae-derived biopolymer comprises a loss circulation material. 62.The composition according to claim 50 wherein the vehicle is chosen fromthe group consisting of water based fluids and solid mediums.